Method and Apparatus for Incrementally Stretching a Web

ABSTRACT

A method and apparatus is provided which uses activation members for incrementally stretching a web at a low strain rate. The activation members include an activation belt and a single activation member wherein the activation belt and single activation member comprise a plurality of teeth and grooves that complement and engage one another at a depth of engagement in a deformation zone. The depth of engagement can be controlled to increase linearly over at least a portion of the deformation zone such that a web interposed between the activation belt and the single activation member in the deformation zone is incrementally stretched at a low rate of strain.

FIELD OF THE INVENTION

A method and apparatus is provided for incrementally stretching a web.In particular, the method and apparatus is directed to controlledincremental stretching of a web at a low rate of strain resulting inimproved web properties with minimal web damage.

BACKGROUND OF THE INVENTION

Nonwoven fabrics or webs, alone or as a laminate with other nonwovens orfilms, constitute all or part of numerous commercial products includingdisposable absorbent products such as adult incontinence products,sanitary napkins, disposable diapers, and training pants. Othercommercial products include wipers, protective garments, and surgicalgowns. Nonwoven fabrics have been used in the manufacture of suchpersonal care products because it is possible to produce them withdesirable cloth-like aesthetics at a low cost. The elastic properties ofsome nonwoven fabrics have allowed them to be used in form-fittinggarments, and their flexibility enables the wearer to move in a normal,unrestricted manner.

Nonwoven fabrics or webs have a physical structure of individual fibers,strands or threads which are interlaid, but not in a regular,identifiable manner as in a knitted or woven fabric. The fibers may becontinuous or discontinuous, and are frequently produced fromthermoplastic polymer or copolymer resins from the general classes ofpolyolefins, polyesters and polyamides, as well as numerous otherpolymers. Fibers from blends of polymers or conjugate multicomponentfibers may also be employed. Methods and apparatus for forming fibersand producing a nonwoven web from synthetic fibers include meltblowing,spunbonding and carding. Physical properties such as strength, softness,elasticity, absorbency, flexibility and breathability are readilycontrolled in making nonwovens. However, certain properties must oftenbe balanced against others. An example would be an attempt to lowercosts by decreasing fabric basis weight while maintaining reasonablestrength.

Films are another common component in many commercial products such astrash bags, diaper backsheets, packaging materials, elastic components,and apertured films such as topsheets. Other films are used as abreathable barrier layer for increased comfort. Breathable microporousfilms comprise filled films which include a thermoplastic polymer andfiller. These and other films can be formed by any one of a variety offilm forming processes known in the art including extruding, casting orblowing.

It is widely recognized that properties relating to strength, softness,stretch and/or extensibility of nonwoven fabrics and films are desirablefor many applications. Softness can be improved by various mechanicalsteps including stretching of the nonwoven to break secondary bonds thattend to stiffen the material. Stretch or extensibility of the materialcan also be improved by stretching the web as it passes betweenactivation rolls. Activation rolls have teeth and grooves whichintermesh at a nip having an activation path length. Typical roll onroll activation tooling have an activation path length in the range of0.5 inches or less. Commercial film, nonwoven, and product makingprocesses are often desired to be run at the highest possible linespeeds to create lower manufacturing costs. As a result, stretchingresulting from the activation can occur at high rates of strain, whichdepending on the nature of the material, can result in damage to thefinal product.

With the ever increasing drive to reduce material cost, the industry iscontinuously looking for ways of reducing basis weight or substitutinglower cost materials in consumer products while maintaining desirableproperties such as strength, softness, elasticity, absorbency,flexibility and breathability. Materials typically lacking suchproperties can attain them through activation; however, some materialsincluding some polypropylenes, polyethylenes, polyesters, andcellulosics are unable to withstand the high rate of strain required forcommercial production. Therefore, the need exists for processes andequipment capable of performing mechanical activation on low costmaterials at relatively high processing line speeds.

SUMMARY OF THE INVENTION

The present invention provides a method and apparatus which usesactivation members for incrementally stretching a web at a relativelylow strain rate. The activation members include an activation belt and asingle activation member wherein the activation belt and singleactivation member comprise a plurality of teeth and grooves thatcomplement and engage one another at a depth of engagement in adeformation zone. The depth of engagement is capable of increasinglinearly over the deformation zone. In exemplary embodiments thedeformation zone can be controlled to increase linearly over at least aportion of the deformation zone such that a web interposed between theactivation belt and the single activation member in the deformation zoneis incrementally stretched at a low rate of strain. The activationmembers are capable of forming deformation zones having a relativelylonger path length while occupying limited space in a machine direction.

In one embodiment, the single activation member is a single activationroll having a plurality of circumferential teeth and grooves. In thisembodiment, the deformation zone is formed between a first section of aplurality of teeth and grooves of the activation belt and an arcuatesection of a plurality of circumferential teeth and grooves of thesingle activation roll which engage one another at a depth ofengagement. A series of back-up rollers are arranged along thedeformation zone forcing the first section of the plurality of teeth andgrooves of the activation belt into engagement with the arcuate sectionof the plurality of circumferential teeth and grooves of the singleactivation roll and controlling the depth of engagement therebetween. Inan alternate embodiment, at least two of the back-up rollers areindependently adjustable to control the depth of engagement. In anotherembodiment, the back-up rollers are arranged to control the depth ofengagement to increase linearly over at least a portion of thedeformation zone, such that a web interposed between the activation beltand the single activation roll in the deformation zone is incrementallystretched at a constant rate of strain.

In another embodiment, the activation belt is a first activation beltand the single activation member is a second activation belt comprisinga plurality of teeth and grooves that complement the plurality of teethand grooves of the first activation belt. A deformation zone having apath length is formed between a first section of a plurality of teethand grooves of the first activation belt and a second section of aplurality of teeth and grooves of the second activation belt. For thisembodiment, a first set of rollers supporting the first section of thefirst activation belt and a second set of rollers supporting the secondsection of the second activation belt are arranged along the path lengthof the deformation zone to force the plurality of teeth and grooves ofthe first activation belt into engagement with the plurality of teethand grooves of the second activation belt and to control the depth ofengagement therebetween. In one embodiment, at least two rollersdisposed at different locations along the path length are independentlyadjustable to change the depth of engagement in the deformation zone. Inanother embodiment the first set of rollers and the second set ofrollers are arranged to provide a linear increase in the depth ofengagement over at least a portion of the deformation zone such that aweb interposed between the first activation belt and the secondactivation belt in the deformation zone is incrementally stretched at aconstant rate of strain.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is photograph of a film activated via high strain rateactivation.

FIG. 1B is a photograph of a film activated via low strain rateactivation.

FIG. 2 is a plan view of an apparatus for incrementally stretching a webaccording to the present invention comprising a single activation rolland an activation belt.

FIG. 3 is a perspective view of the apparatus shown in FIG. 2.

FIG. 4 is a plan view of an apparatus for incrementally stretching a webaccording to the present invention comprising a first activation beltand a second activation belt.

FIG. 5A is a perspective view of the apparatus shown in FIG. 4.

FIG. 5B is a close up view of a portion of the apparatus shown in FIG.5A showing the teeth and grooves of the first and second activationbelts.

FIG. 6 is a cross sectional view of an activation belt used in theapparatus shown in FIGS. 2-5B.

FIG. 7A is a perspective view showing portions of activation membersaccording to the present invention showing teeth and grooves arranged ina machine direction for incrementally stretching a web in the crossmachine direction.

FIG. 7B is a perspective view showing portions of activation membersaccording to the present invention showing teeth and grooves arranged ina cross machine direction for incrementally stretching a web in themachine direction.

FIG. 8 is an enlarged, fragmentary, cross-sectional view showing theinterengagement of teeth and grooves of activation members as shown inFIG. 7A and FIG. 7B.

FIG. 9 is an even further enlarged view of the activation members shownin FIG. 7A and

FIG. 7B showing several interengaged teeth and grooves with a web ofmaterial therebetween.

FIG. 10A is a graph comparing the increase in depth of engagement vs.time for activation belts according to the present invention andintermeshing ring rolls.

FIG. 10B is a graph comparing the rate of change of engagement vs.engagement for activation belts according to the present invention andintermeshing ring rolls.

FIG. 11 is a perspective view showing portions of activation membersaccording to the present invention for use in a SELF process.

FIG. 12 is a schematic representation of a web after it has passedbetween a pair of inter-meshing SELF rolls.

FIG. 13 is a pattern that can be produced in a web by passing the webbetween a pair of intermeshing SELF activation members.

FIG. 14 is a pattern that can be produced in a web by passing the webbetween a pair of intermeshing SELF activation members.

FIG. 15 is a perspective representation of an activation member for usein a micro-SELF apparatus.

FIG. 16 is an enlarged perspective representation of the teeth on amicro-SELF activation member.

FIG. 17 is a graph showing strain rate varying from low to high in thedeformation zone during micro-SELF activation.

FIG. 18A is a tuft formed in a laminate via micro-SELF activationaccording to the strain rate depicted by the graph in FIG. 17.

FIG. 18B is a tuft formed during micro-SELF activation using high strainrate activation rolls.

FIG. 19 is a graph showing strain rate varying from high to low in thedeformation zone during micro-SELF activation.

FIG. 20A is a tuft formed in a laminate via micro-SELF activationaccording to the strain rate depicted by the graph in FIG. 19.

FIG. 20 B is a tuft formed during micro-SELF activation using highstrain rate activation rolls.

FIG. 21 is a schematic representation of activation members configuredfor a rotary knife aperturing.

FIG. 22 is a perspective view of a rotary knife aperturing activationmember.

FIG. 23A is an enlarged view of the rotary knife aperturing activationmember shown in FIG. 22.

FIG. 23B is an enlarged view of a tooth on the rotary knife aperturingactivation member shown in FIG. 22.

DETAILED DESCRIPTION OF THE INVENTION Definitions

As used herein and in the claims, the term “comprising” is inclusive oropen-ended and does not exclude additional unrecited elements,compositional components, or method steps.

As used herein, “machine direction” means the path that material, suchas a web, follows through a manufacturing process.

As used herein “cross direction” means the path that is perpendicular tothe machine direction in the plane of the web.

As used herein the term “activation” means any process by which tensilestrain produced by intermeshing teeth and grooves causes intermediateweb sections to stretch or extend. Such processes have been found usefulin the production of many articles including breathable films, stretchcomposites, apertured materials and textured materials. For nonwovenwebs, the stretching can cause fiber reorientation, a reduction in basisweight, and/or controlled fiber destruction in the intermediate websections. For example, a common activation method is the process knownin the art as ring rolling.

As used herein the term “activation member” means a device includingteeth and grooves for performing activation.

As used herein the term “deformation zone” means an area where teeth andgrooves of opposing activation members intermesh causing activation.

As used herein the term “path length” means the length of thedeformation zone formed by intermeshing teeth and grooves of opposingactivation members.

As used herein “depth of engagement” means the extent to whichintermeshing teeth and grooves of opposing activation members extendinto one another.

As used herein, the term “nonwoven web” refers to a web having astructure of individual fibers or threads which are interlaid, but notin a repeating pattern as in a woven or knitted fabric, which do nottypically have randomly oriented fibers. Nonwoven webs or fabrics havebeen formed from many processes, such as, for example, meltblowingprocesses, spunbonding processes, hydroentangling, and bonded carded webprocesses, including carded thermal bonding. The basis weight ofnonwoven fabrics is usually expressed in grams per square meter (gsm).The basis weight of the laminate web is the combined basis weight of theconstituent layers and any other added components. Fiber diameters areusually expressed in microns; fiber size can also be expressed indenier, which is a unit of weight per length of fiber. The basis weightof laminate webs suitable for use in the present invention can rangefrom 6 gsm to 400 gsm, depending on the ultimate use of the web. For useas a hand towel, for example, both a first web and a second web can be anonwoven web having a basis weight of between 18 gsm and 500 gsm.

The constituent fibers of a nonwoven web can be polymer fibers, and canbe monocomponent, bicomponent, and/or biconstituent, non-round (e.g.,capillary channel fibers), and can have major cross-sectional dimensions(e.g., diameter for round fibers) ranging from 0.1-500 microns. Theconstituent fibers of the nonwoven web may also be a mixture ofdifferent fiber types, differing in such features as chemistry (e.g. PEand PP), components (mono- and bi-), denier (micro denier and >20denier), shape (i.e. capillary and round) and the like. The constituentfibers can range from about 0.1 denier to about 100 denier.

As used herein, “spunbond fibers” refers to relatively small diameterfibers which are formed by extruding molten thermoplastic material asfilaments from a plurality of fine, usually circular capillaries of aspinneret with the diameter of the extruded filaments then being rapidlyreduced. Spunbond fibers are generally not tacky when they are depositedon a collecting surface. Spunbond fibers are generally continuous andhave average diameters (from a sample of at least 10) larger than 7microns, and more particularly, between about 10 and 40 microns.

As used herein, the term “meltblowing” refers to a process in whichfibers are formed by extruding a molten thermoplastic material through aplurality of fine, usually circular, die capillaries as molten threadsor filaments into converging high velocity, usually heated, gas (forexample air) streams which attenuate the filaments of moltenthermoplastic material to reduce their diameter, which may be tomicrofiber diameter. Thereafter, the meltblown fibers are carried by thehigh velocity gas stream and are deposited on a collecting surface,often while still tacky, to form a web of randomly dispersed meltblownfibers. Meltblown fibers are microfibers which may be continuous ordiscontinuous and are generally smaller than 10 microns in averagediameter.

As used herein, the term “polymer” generally includes, but is notlimited to, homopolymers, copolymers, such as for example, block, graft,random and alternating copolymers, terpolymers, etc., and blends andmodifications thereof. In addition, unless otherwise specificallylimited, the term “polymer” includes all possible geometricconfigurations of the material. The configurations include, but are notlimited to, isotactic, atactic, syndiotactic, and random symmetries.

As used herein, the term “monocomponent” fiber refers to a fiber formedfrom one or more extruders using only one polymer. This is not meant toexclude fibers formed from one polymer to which small amounts ofadditives have been added for coloration, antistatic properties,lubrication, hydrophilicity, etc. These additives, for example titaniumdioxide for coloration, are generally present in an amount less thanabout 5 weight percent and more typically about 2 weight percent.

As used herein, the term “bicomponent fibers” refers to fibers whichhave been formed from at least two different polymers extruded fromseparate extruders but spun together to form one fiber. Bicomponentfibers are also sometimes referred to as conjugate fibers ormulticomponent fibers. The polymers are arranged in substantiallyconstantly positioned distinct zones across the cross-section of thebicomponent fibers and extend continuously along the length of thebicomponent fibers. The configuration of such a bicomponent fiber maybe, for example, a sheath/core arrangement wherein one polymer issurrounded by another, or may be a side-by-side arrangement, a piearrangement, or an “islands-in-the-sea” arrangement.

As used herein, the term “biconstituent fibers” refers to fibers whichhave been formed from at least two polymers extruded from the sameextruder as a blend. Biconstituent fibers do not have the variouspolymer components arranged in relatively constantly positioned distinctzones across the cross sectional area of the fiber and the variouspolymers are usually not continuous along the entire length of thefiber, instead usually forming fibers which start and end at random.Biconstituent fibers are sometimes also referred to as multiconstituentfibers.

As used herein, the term “non-round fibers” describes fibers having anon-round cross-section, and include “shaped fibers” and “capillarychannel fibers.” Such fibers can be solid or hollow, and they can betri-lobal, delta-shaped, and are preferably fibers having capillarychannels on their outer surfaces. The capillary channels can be ofvarious cross-sectional shapes such as “U-shaped”, “H-shaped”,“C-shaped” and “V-shaped”. One preferred capillary channel fiber isT-401, designated as 4 DG fiber available from Fiber InnovationTechnologies, Johnson City, Tenn. T-401 fiber is a polyethyleneterephthalate (PET polyester).

Regarding all numerical ranges disclosed herein, it should be understoodthat every maximum numerical limitation given throughout thisspecification includes every lower numerical limitation, as if suchlower numerical limitations were expressly written herein. In addition,every minimum numerical limitation given throughout this specificationwill include every higher numerical limitation, as if such highernumerical limitations were expressly written herein. Further, everynumerical range given throughout this specification will include everynarrower numerical range that falls within such broader numerical rangeand will also encompass each individual number within the numericalrange, as if such narrower numerical ranges and individual numbers wereall expressly written herein.

Materials such as polypropylenes, polyethylenes, polyesters, andcellulosics are typically damaged or even shredded when subjected tohigh strain rates during activation. For instance, FIG. 1A illustrates aClopay 15 gsm polypropylene film that has been activated at 100 feet perminute using activation rolls. As shown the film exhibits noticeablesigns of damage evidenced by the presence of holes in the film. Thepresent invention provides an apparatus and method for deforming webmaterials by incrementally stretching a web via activation causingminimal, if any, destruction of the web. The method and apparatusinclude opposing activation members comprising a plurality of teeth andgrooves that complement and engage one another at a depth of engagementin a deformation zone having a path length. The path length is sized andthe depth of engagement is controlled such that a web interposed betweenthe activation members in the deformation zone is incrementallystretched at a relatively low rate of strain with respect to known rollon roll activation tooling. FIG. 1B illustrates the Clopay 15 gsmpolypropylene film shown in FIG. 1A, activated according to the lowstrain rate method of the present invention at 500 feet per minute. Asshown, even at higher web speed, the web experienced no visible damageas compared to the web in FIG. 1A. Web materials suitable for activationaccording to the present invention include, but are not limited topolymeric film materials, nonwoven web materials, and laminates ofnonwoven webs with other nonwoven webs and/or polymeric film materials.Other web materials suitable for activation include paper, cellulose,wovens, natural (sustainable) materials, metallic foils, foams,elastics, absorbent batting and the like.

The low strain rate activation according to the present invention willbe described with reference to the following figures which illustratecertain embodiments. It will be apparent to those skilled in the artthat these embodiments do not represent the full scope of the inventionwhich is broadly applicable in the form of variations and equivalents asmay be embraced by the claims appended hereto. Furthermore, featuresdescribed or illustrated as part of one embodiment may be used withanother embodiment to yield still a further embodiment. It is intendedthat the scope of the claims extend to all such variations andequivalents.

FIG. 2 illustrates an exemplary apparatus for incrementally stretching aweb via activation according to the present invention. Apparatus 110comprises a single activation member in the form of a single activationroll 112 and an activation belt 114. The single activation roll 112comprises a cylindrical roll and the activation belt 114 comprises acontinuous endless band. As shown in FIG. 2, web 116 is withdrawn from asupply roll 118 and travels in a direction indicated by the arrow. Web116 is fed to deformation zone 120 formed between the single activationroll 112 and the activation belt 114 where the web is incrementallystretched as it passes therebetween.

The relative positions of the single activation roll 112 and activationbelt 114 are shown in a perspective view in FIG. 3. The singleactivation roll 112 is rotatably mounted on a power driven rotatableshaft. The single activation roll 112 comprises a cylindrical outersurface 122 including a plurality of axially-spaced, side-by-side,circumferentially-extending equally-configured teeth 124 formed therein.The teeth 124 can be in the form of thin fins of substantiallyrectangular cross section, or they can have a triangular or an invertedV-shape when viewed in cross section. If they are triangular, thevertices of the teeth 124 are outermost with respect to the cylindricalouter surface 122 of the single activation roll 112. In anyconfiguration, the outermost tips of the teeth 124 are preferablyrounded to avoid cuts or tears in the web materials. The spaces betweenadjacent teeth define recessed, circumferentially-extending, equallyconfigured grooves 126. The grooves 126 can be of substantiallyrectangular cross section when the teeth are of substantiallyrectangular cross section, and they can be of inverted triangular crosssection when the teeth are of triangular cross section.

The activation belt 114 is disposed contiguous with the singleactivation roll 112. The activation belt 114 includes an outer surface127 comprising a plurality of axially-spaced, side-by-side,longitudinally-extending equally-configured teeth 128 and grooves 130which complement the plurality of circumferential teeth 124 and grooves126 of the single activation roll 112. Thus, the activation belt 114 andthe single activation roll 112 include a plurality of spaced teeth andalternating grooves between each pair of adjacent teeth. The teeth andthe grooves need not each be of the same shape as long as there issufficient clearance to permit the material that passes between theinterengaged activation members to be received within the respectivegrooves and to be locally stretched, as will be explained further below.

The activation belt 114 can include urethane-based material in thedurometer range of 80 A-85 D, ground to a belt profile specificationshown in FIG. 6 where the activation belt has a width W of about 1.200inches (30.48 mm), a thickness T of about 0.215 inches (5.461 mm), atooth height TH of about 0.090 inches (2.286 mm) and a tooth pitch P ofabout 0.060 inches (1.524 mm). In the embodiment shown in FIGS. 2 and 3,two or more belts arranged in parallel can be used depending on thecross machine direction length of the web that is incrementallystretched. For this reason, the distance D between the edges of the beltshown in FIG. 6 and the first tooth inside each edge is half the pitchor 0.030 inches (0.762 mm). Such belts are supplied by F.N. Sheppard &Co. of 1261 Jamike Drive Erlanger, Ky. 41018.

The activation belt 114 includes an inner surface 132 which is fitted onthree pulleys, a first pulley 134 a, a second pulley 134 b, and a thirdpulley 134 c. The three pulleys are disposed near the single activationroll 112 in a triangular arrangement. The first pulley 134 a is poweredto drive the activation belt 114 along the three pulleys 134 a, 134 band 134 c. The second and the third pulleys 134 b and 134 c are idlersguiding the activation belt 114 along a defined path which engages theteeth 128 and grooves 130 of the activation belt 114 with thecircumferential teeth 124 and grooves 126 of the single activation roll112. The corresponding teeth 128 and grooves 130 of the activation belt114 and the single activation roll 112 engage along an arcuate section142 of the single activation roll 112 forming the deformation zone 120where, as previously described, the web 116 is incrementally stretchedas it is conveyed therebetween. The first, second, and third pulleys 134a, 134 b, and 134 c include shoulders 136 for maintaining axialalignment of the activation belt 114.

The second pulley 134 b includes an adjustment 138 to vary the tensionon the activation belt 114. Belt tension can be adjusted wherein a web116 conveyed between the single activation roll 112 and the activationbelt 114 causes the activation belt 114 to deflect away from the singleactivation roll 112 thereby preventing the plurality of teeth 128 andgrooves 130 of the activation belt 114 from engaging the circumferentialteeth 124 and grooves 126 of the single activation roll 112. Theactivation belt 114 tension can vary depending on the material of theweb 116.

In another embodiment (not shown), instead of three pulleys, theapparatus could include two pulleys disposed in the locations of pulleys134 a and 134 c where each pulley is large enough in diameter andpositioned to eliminate the need of the third tensioning pulley 134 b.Alternatively, additional pulleys or idlers can be added and disposed tosupport the belt in an elliptical or circular arrangement in order toincrease belt life by reducing belt flex during operation.

The teeth 128 and grooves 130 of the activation belt 114 are forced intoengagement with the circumferential teeth 124 and grooves 126 of thesingle activation roll 112, deforming the web 116 therebetween, by aseries of back-up rollers 140(a-e) arranged along an arcuate section 142of the outer surface 122 of the single activation roll 112 with theactivation belt 114 passing therebetween. The back-up rollers 140(a-e)form the deformation zone 120 where the activation belt 114 is forcedinto engagement with the single activation roll 112. The back-up rollers140(a-e) can be adjustable to vary the radial distance between theback-up rollers and the outer surface 122 of the single activation roll112. The radial adjustment controls the depth of engagement between theteeth 128 and grooves 130 of the activation belt 114 and thecircumferential teeth 124 and grooves 126 of the single activation roll112.

The back-up rollers 140(a-e) can be arranged along the deformation zone120 and independently adjusted to control the depth of engagementbetween the activation belt 114 and the single activation roll 112 ateach back-up roller 140(a-e) to incrementally stretch the web 116conveyed through the deformation zone 120. In an exemplary embodiment,the series of back-up rollers 140(a-e) can be adjusted to increase thedepth of engagement linearly along the deformation zone 120 resulting ina constant low rate of strain induced on the deforming web. For thisembodiment, the radial distance between the first back-up roller 140 ain the series and the outer surface 122 of the single activation roll112 is adjusted to a maximum distance where as the radial distancebetween the last back-up roller 140 e in the series and the outersurface 122 of the single activation roll 112 is adjusted to a minimumdistance. The radial distance between the outer surface 122 of thesingle activation roll 112 and the back-up rollers 140(b-d) disposedbetween the first and last roller 140 a and 140 e in the series areadjusted to decrease an amount for each succeeding roller from the firstback-up roller to the last back-up roller resulting in a smoothcontinuous increase in depth of engagement.

The number of back-up rollers used depends on the path length of thedeformation zone 120 and the size of the individual rollers. Since theactivation belt 114 can deflect between the individual back-up rollers140(a-e) during deformation of the web, it may be desirable to minimizethe diameter of the back-up rollers 140(a-e) to minimize thecorresponding distance between rollers. In an alternate embodiment (notshown), a back-up belt can be added to the back-up rollers to furtherreduce activation belt deflection between the individual back-uprollers. For this embodiment, a back-up belt can be assembled on theback-up rollers and work in conjunction with the back-up rollers tocontrol the depth of engagement between the activation belt and thesingle activation roll while reducing the deflection of the activationbelt between back-up rollers.

In order to prevent the web from slipping in the cross machine directionand corrugating during activation, the web can be prewrapped on thesingle activation roll prior to the deformation zone. Such embodimentcan include a nip roll (not shown) disposed adjacent to the singleactivation roll prior to the deformation zone to add tension to the webduring activation.

In another embodiment (not shown), the activation belt can include alaminate structure comprised of a grooved upper layer and a relativelystiffer backing layer to minimize the deflection of the activation belt.In alternate embodiment, the activation belt may consist of flexiblyjoined rigid links, continuously extruded shaped belts, spun-cast belts,molded belts, and other known belt technologies. Other means ofsupporting the activation belt include dead plates, reinforcing wires,chains, conveyors and the like.

The activation belt can also include designs to increase durability andlongevity. Such designs include increasing the coefficient of frictionof the inner diameter of the belt to reduce slippage between the beltand pulleys such that tension ordinarily placed on the belt to controlslippage can be reduced. Alternatively, the pulleys can be replaced withgears and the inner diameter of the belt can include mating gears. Otherdesign for improving belt durability and longevity include varying thedurometer through the thickness of the belt so that the inner diameterof the belt is soft to enhance flexibility while the teeth in the outerdiameter are hard providing robustness during activation. Anotheralternative belt design can include producing belts where the teeth areunder an initial tension prior to assembly which is enhanced atassembly. The pretensioned teeth can be produced by forming theactivation teeth on the inner diameter of the belt during manufactureand turning the belt inside out prior to assembly so that the teeth areopposite the belt surface mating with the pulleys. Since the teeth arenormally loaded in compression in the deformation zone, designing thebelt with an initial tensile load can increase the tension such thatteeth approach a neutral load in the deformation zone instead of anegative compressive load.

The path length of the deformation zone 120 is set to accommodate webspeed which is the speed the web flows in the machine direction duringprocessing. The path length can be increased with increasing line speedin order to maintain a relatively lower rate of strain. Potential damageto the web can minimized in this manner without reducing line speed,increasing apparatus size and/or decreasing engagement. Although thepath length of the deformation zone 120 for the activation belt andsingle activation roll apparatus 110 can vary, the path length islimited by the size of the single activation roll 112. For the presentinvention, the size of the single activation roll 112 can vary from aroll having an outside diameter ranging from about 3.0 inches (0.076meters) to about 96.0 inches (2.438 meters) and the corresponding pathlength of the deformation zone 120 can vary from about 0.5 inches (0.013meters) to about 200 inches (5.08 meters).

Depending on the type of material to be activated and processrequirements such as line speed, it may be desirable to maximize thepath length of the deformation zone 120. Such requirements can beachieved by sizing the activation roll 112 and providing a number ofback-up rollers 140 necessary to accomplish the desired path length.However, meeting such requirements may require a nonstandard roll sizewhich can be costly or impractical for a manufacturing line. Forinstance, space available on web manufacturing lines for devices such asthe single activation roller and activation belt apparatus 110previously described can be limited. In fact it is desirable for suchapparatus to occupy a space on the line having a length in the machinedirection which is less than about 39 inches (1 meter). Such spacerequirements can limit the size of the single activation roll 112 to 24inches (0.61 meters) resulting in maximum deformation zone 120 pathlength of about 50 inches (1.27 meters). Therefore, it is desirable forthe deformation zone 120 path length of the activation belt and singleroller activation apparatus 110 to range from about 0.5 inches (0.01meters) to about 50 inches (1.27 meters) and from about 10 inches (0.25meters) to about 50 inches (1.27 meters). Applications requiring longerpath lengths can be accomplished using alternative embodiments of thepresent invention such as the dual activation belt apparatus 210illustrated in FIG. 4.

The dual activation belt apparatus 210 includes an activation belt inthe form of a first activation belt 212 and a single activation memberin the form of a second activation belt 214. The first and secondactivation belts 212, 214 comprise continuous bands. As shown in FIG. 4,web 216 is withdrawn from a supply roll 218 and travels in a directionindicated by the arrow. Web 216 is fed to deformation zone 220 formed bythe first activation belt 212 and the second activation belt 214 wherethe web is incrementally stretched as it passes therebetween.

The relative positions of the first activation belt 212 and secondactivation belt 214 are shown in a perspective view in FIG. 5A. Thefirst and second activation belts 212, 214 include a plurality ofaxially-spaced, side-by-side, longitudinally-extending,equally-configured teeth 224, 226 shown in FIG. 5B. Teeth 224, 226 canbe in the form of thin fins of substantially rectangular cross section,or they can have a triangular or an inverted V-shape when viewed incross section. If they are triangular, the vertices of teeth areoutermost with respect to the outer surface of the belts. The spacesbetween adjacent teeth 224, 226 shown in FIG. 5B define recessed,circumferentially-extending, equally configured grooves 228, 230. Thegrooves 228, 230 can be of substantially rectangular cross section whenthe teeth 224, 226 are of substantially rectangular cross section, andthey can be of inverted triangular cross section when the teeth 224, 226are of triangular cross section. Thus, the first and second activationbelts 212, 214 include a plurality of spaced teeth 224, 226 andalternating grooves 228, 230 between each pair of adjacent teeth.

As shown in FIGS. 4 and 5A, the dual belt apparatus 210 includes a lowercarriage 232 supporting the first activation belt 212 and an uppercarriage 240 supporting the second activation belt 214. Lower carriage232 includes a lower idler bed 234 and upper carriage 240 includes upperidler bed 242. The lower idler bed 234 includes a lower or first set ofrollers 236 which support the first activation belt 212 and the upperidler bed 242 includes an upper or second set of rollers 244 whichsupport the second activation belt 214. Rollers 236 and 244 support thefirst and second activation belts 212, 214 in a parallel arrangement andforce the teeth 224, 226 and grooves 228, 230 into engagement in thedeformation zone 220. Rollers 236 and 244 can be independently adjustedto control the depth of engagement between teeth 224, 226 and grooves228, 230 of the first and second activation belts 212, 214. Other meansof supporting the activation belts include dead plates, reinforcingwires, chains, conveyors and the like.

The lower carriage 232 includes three pulleys, a first pulley 238 a, asecond pulley 238 b and a third pulley 238 c disposed in a triangulararrangement and supporting the first activation belt 212. The firstpulley 238 a is rotatably mounted on power driven shaft and the secondand the third pulleys 238 b, 238 c are rotatably mounted on idlershafts. The three pulleys guide the first activation belt 212 along adefined path which passes over rollers 236 and include shoulders 235 formaintaining axial alignment of the first activation belt 212. The firstactivation belt 212 is loaded with sufficient tension to drive the beltover the pulleys and lower set of rollers without slipping.

Similar to the lower carriage 232, the upper carriage 240 includes threepulleys, a fourth pulley 246 a, a fifth pulley 246 b and a sixth pulley246 c disposed in a triangular arrangement opposite the lower carriage232. The fourth pulley 246 a is rotatably mounted on power driven shaftand fifth and sixth pulleys 246 b, 246 c are rotatably mounted on idlershafts. The fourth, fifth and sixth pulleys 246(a-c) guide the secondactivation belt 214 along a defined path which passes over the upper setof rollers 244 and include shoulders 235 for maintaining axial alignmentof the second activation belt 214. Like the first activation belt 212,the second activation belt 214 is loaded with sufficient tension todrive the belt over the pulleys and upper set of rollers 244 withoutslipping.

In another embodiment (not shown), the activation belts can includelaminate structures comprised of a grooved upper layer and a relativelystiffer backing layer to minimize the deflection of the activationbelts. In alternate embodiment, the activation belts may consist offlexibly joined rigid links, continuously extruded shaped belts,spun-cast belts, molded belts, and other known belt technologies. Theactivation belts can also include designs to increase durability andlongevity previously described relative to the single activation roll112 and activation belt 114 embodiment illustrated in FIGS. 2 and 3.

For embodiment shown in FIGS. 4 and 5A, the first and second activationbelts can include urethane-based material in the durometer range of 80A-85 D, ground to a belt profile specification shown in FIG. 6 where theactivation belt has a width W of about 1.200 inches (30.48 mm), athickness T of about 0.215 inches (5.461 mm), a tooth height TH of about0.090 inches (2.286 mm) and a tooth pitch P of about 0.060 inches (1.524mm). In the embodiments shown in FIGS. 4 and 5A, two or more belts canbe assembled on the pulleys of the upper and lower chassis depending onthe cross machine direction length of the web. For this reason, thedistance D between the edges of the belt shown in FIG. 6 and the firsttooth inside each edge is half the pitch or 0.030 inches (0.762 mm).Such belts are supplied by F.N. Sheppard & Co. of 1261 Jamike DriveErlanger, Ky. 41018.

In order to secure the edges of the web 216 and prevent slippage in thecross machine direction and corresponding corrugating duringdeformation, the upper carriage 240 can include hold down belts 248which span the length of the deformation zone 220 and the lower carriagecan include hold down belts 252 which oppose hold down belts 248 on theupper carriage 240. Hold down belts 248 and 252 sandwich the web 216 andexert normal forces along the web edges during deformation. As shown inFIG. 5A, hold down belt 248 are assembled on opposing sides of the upperset of rollers 244 along the deformation zone 220 and hold down belts252 are assembled on opposing sides of rollers 236 along the deformationzone 220. Hold down belts 248 are assembled on pulleys 250 a, 250 bmounted to the upper carriage 240 while hold down belts 252 areassembled on pulleys 254 a and 254 b mounted to the lower carriage 232.The pulleys supporting the hold down belts enable the belts to travelalong with the web during incremental stretching. For the embodimentshown in FIGS. 3 and 4A, commercially available V-profile belting can beused as hold down belts, such as, Eagle Belting, Profile 3L, Part Number1032030 supplied by Fenner Drives of 311 West Stiegel Street Manheim,Pa. 17545. Other means for preventing lateral slippage of the web knownin the art can be used such as those disclosed in U.S. Pat. No.5,143,679 entitled “Method for Sequentially Stretching Zero StrainStretch Laminate Web to Impart Elasticity thereto Without Rupturing theWeb,” which issued on Sep. 1, 1992, to Weber, et al.

As described above, the rollers forming the lower and upper set ofrollers 236, 244 supporting the first and second activation belts 212,214 can be independently adjusted to control the depth of engagementbetween the teeth and grooves of the corresponding belts in thedeformation zone 220. Rollers 236, 244 can be arranged such that eachroller forming the lower set of rollers 236 is disposed directlyopposite a roller forming the upper set of rollers 244 with a distancetherebetween. The distance between each opposing pairs of rollers can beadjusted to smoothly and continuously control the depth of engagement byadjusting the vertical position of one or both rollers forming anopposing pair.

In an alternate embodiment, the depth of engagement can be controlled byvarying the vertical orientation of the upper carriage 240 whilemaintaining the orientation of the lower carriage 232 in a fixedposition. For this embodiment, the first and second sets of rollers 236,244 are rotatably mounted on the corresponding idler beds 234, 242 infixed orientations. The upper carriage 240 is vertically adjustable toraise and lower the upper idler bed 242 while the lower idler bed 234remains fixed. By raising and lowering the upper idler bed 242, thedistance between the lower set of rollers 236 and the upper set ofrollers 244 and the corresponding depth of engagement between the teeth224, 226 and grooves 228, 230 of the first and second activation belts212, 214 can be adjusted. For this embodiment, the vertical position ofthe upper carriage 240 can be controlled by an air or hydraulic cylinder260 which raises and lowers the upper carriage 240 when actuated.Positive mechanical stops can be positioned to set the initialorientation of the upper carriage 240 in a lowered position providing amacro level of adjustment and the initial distance between the lower setof rollers and the opposing upper set of rollers. Adjustable threadedrods 262 and depth gages 264 disposed on opposite ends of the upperidler bed 242 provide micro level adjustment of the depth of engagementbetween the first and second activation belts 212, 214. The adjustablethreaded rods 262 can be adjusted such that the distance between theopposing rollers at the entrance of the deformation zone 220 ismaximized providing minimal or zero depth of engagement between theteeth 224, 226 and grooves 228, 230 of the first and second activationbelts 212, 214 and the distance between the opposing rollers at the exitof the deformation zone is minimized providing maximum depth ofengagement between the teeth and grooves of the first and secondactivation belts 212, 214. With this arrangement the pitch of the upperidler bed 242 supporting the upper set of rollers 244 can be oriented toprovide a linear increase in the depth of engagement from the entranceof the deformation zone 220 to the exit of the deformation zone 220.

The activation belt and single activation roller apparatus and the dualactivation belt apparatus previously described can be used wholly orpartly in place of traditional roll on roll processes. For example, theapparatus and method of the present invention can be used in combinationwith a thermal melt weakening step to produce apertures, as disclosed inU.S. Pat. No. 5,628,097 and U.S. Pat. No. 5,916,661, and US2003/0028165A1. As well, the apparatus and method of the presentinvention can be used for making stretch portions of a topsheet asdisclosed in US 2004/0127875A1, filed Dec. 18, 2002. Similarly, theapparatus and method of the present invention can be used to producebeneficially-modified topsheets as disclosed in US 2004/0131820A1, WO2004/059061A1 and WO 2004/058118A1, and to produce apertured formedfilms, nonwoven webs, and laminates, as disclosed in US 2005/021753.Absorbent cores can also be modified as disclosed in WO 2004/058497A1 inwhich a laminate of two webs is made by processing two webs together toform a fiber-integrated composite absorbent core. In each of theprocesses referenced above, heat can be utilized either before or withinthe deformation zone. As in these prior art references, the patterns inthe activation belt(s) may be continuous or discontinuous and maycomprise zones differing in tooth height, tooth shape, orientationand/or pitch.

One formation means which can be performed using the activation membersof the present invention is a process commonly referred to as ringrolling where intermeshing teeth and grooves engage and incrementallystretch the web interposed therebetween. For ring rolling the activationmembers can be arranged to incrementally stretch the web in the crossmachine direction or the machine direction depending on the orientationof the teeth and grooves. For instance, for incremental stretching inthe cross machine direction CD, teeth 52 and grooves 54 on eachactivation member 40, 42 are oriented in the machine direction MD asshown in FIG. 7A. Conversely, for incremental stretching in the machinedirection MD, the teeth 52 and grooves 54 on each activation member 40,42 are oriented in the cross machine direction CD as shown in FIG. 7B.Belts comprising such cross machine direction teeth and grooves are keptin phase in the machine direction with respect to the intermeshingpattern.

FIG. 8 is an enlarged, fragmentary, cross-sectional view showing theinterengagement of teeth 52 and grooves 54 of respective opposingactivation members 40, 42 in a deformation zone which incrementallystretch the web. Teeth 52 have a tooth height TH and are spaced apartfrom one another by a preferably uniform distance to define a toothpitch P. As shown, teeth 52 of activation 40 member extend partiallyinto grooves 54 of the opposed activation member 42 to define a “depthof engagement”, E, as shown in FIG. 8. During activation, the depth ofengagement is controlled to gradually increase over at least a portionof the deformation zone.

FIG. 9 is an even further enlarged view of several interengaged teeth 52and grooves 54 in the deformation zone with a web 34 of materialtherebetween. As shown, a portion of a web 34, which can be nonwovenweb, is received between the interengaged teeth and grooves in thedeformation zone. The interengagement of the teeth and grooves causeslaterally spaced portions of web 34 to be pressed by teeth 52 intoopposed grooves 54. In the course of passing between activation members,the forces of teeth 52 pressing web 34 into opposed grooves 54 imposewithin web 34 tensile stresses that act in the machine or cross machinedirection depending on the orientation of the teeth and grooves on theactivation members. The tensile stresses can cause intermediate websections 58 that lie between and that span the spaces between the tipsof adjacent teeth 52 to stretch or extend in a machine or cross machinedirection, which can result in a localized reduction of the webthickness at each of intermediate web sections 58. For nonwoven webs,including air laid webs, the stretching can cause fiber reorientation, areduction in basis weight, and controlled fiber destruction in theintermediate web sections 58.

Although the portions of web 34 that lie between the adjacent teeth arelocally stretched, the portions of the web that are in contact with thetips of the teeth may not undergo a similar degree of extension. Becauseof the frictional forces that exist between the surfaces at the roundedouter ends of teeth 52 and the adjacent areas 60 of web 34 that are incontact with the tooth surfaces at the outer ends of the teeth, slidingmovement of those portions of the web surfaces relative to the toothsurfaces at the outer ends of the teeth is minimized Consequently, insome cases, the properties of the web 34 at those areas of the web thatare in contact with the surfaces of the tooth tips change only slightly,as compared with the change in web properties that occur at intermediateweb sections 58.

Because of the localized web stretching of web 34 that has taken place,with the consequent increase in web width or length depending on thedirection of stretch, the web material that exits from the deformationzone formed by the activation members can have a lower basis weight thanthat of the entering web material, provided the exiting material remainsin a substantially flat, laterally extended state. For instance, a webstretched in the cross machine direction may contract laterally to itsoriginal width or length as it exits from the deformation zone, in thatthe web is placed under some tension in the web movement direction, inwhich case the exiting, modified web may have the same basis weight asit had in its entering condition. If, however, the exiting web issubjected to a sufficiently high web machine direction tension, theexiting web can be made to contract to a smaller width than its originalwidth, in which case the web will have a greater basis weight than itsoriginal basis weight. On the other hand, if the web is subjected tosufficient additional cross-web stretching by passing the modified webbetween so-called Mount Hope rolls, tentering frames, angled idlers,angles nips, or the like as described above, the exiting, modified webcan have less than its original basis weight. Thus, by selecting asuitable tooth and groove configuration for the activation members, byselecting a suitable web movement direction tension level, and byselecting whether or not to subject the web to additional cross-webstretching, the resulting modified nonwoven web can have a web widththat can range from about 20% to about 500% of the initial web width anda basis weight that is less than, equal to, or greater than the web'soriginal basis weight.

Teeth 52 can be generally triangular in cross section having generallyrounded tooth tips, as shown in FIGS. 8 and 9. As shown teeth 52 have atooth height TH (note that TH can also be applied to groove depth; inone embodiment tooth height and groove depth can be equal), and atooth-to-tooth spacing referred to as the pitch P. The depth ofengagement E, tooth height TH, and pitch P can be varied as desireddepending on the properties of the webs being processed and the desiredcharacteristics of the processed webs.

As will be appreciated by those skilled in the art, the sizes of therespective teeth and grooves can be varied within a wide range and wouldstill be effective to carry out the present invention. In that regard,additional structural details of suitable activation members accordingto the present invention are provided in U.S. Pat. No. 5,156,793,entitled “Method for Incrementally Stretching Zero Strain StretchLaminate Sheet in a Non-Uniform Manner to Impart a Varying Degree ofElasticity Thereto,” which issued on Oct. 20, 1992, to Kenneth B. Buellet al.; and in U.S. Pat. No. 5,167,897 entitled “Method forIncrementally Stretching a Zero Strain Stretch Laminate Sheet to ImpartElasticity Thereto,” which issued on Dec. 1, 1992, to Gerald M. Weber etal. Other Activation patents include: U.S. Pat. No. 5,527,304, entitled“Absorbent Article with Elasticized Side Panels having Extension Panel,”which issued on Jun. 18, 1996, to Buell; U.S. Pat. No. 5,674,216,entitled “Absorbent Article with Elasticized Side Panels,” which issuedon Oct. 7, 1997, to Buell; U.S. Pat. No. 6,476,289, entitled “Garmenthaving Elastomeric Laminate,” which issued on Jun. 18, 1996, to Buell;U.S. Pat. No. 5,628,741, entitled “Absorbent Article with ElasticFeature having a Prestrained Web Portion and Method for Forming Same,”which issued on May 13, 1997, to Buell; U.S. Pat. No. 5,591,155,entitled “Disposable Training Pant having Improved Stretchable SidePanels,” which issued on Jan. 7, 1997, to Nishikawa; U.S. Pat. No.5,246,433, entitled “Elasticized Disposable Training Pant and Method ofmaking the Same,” which issued on Sep. 21, 1993, to Hasse; U.S. Pat. No.5,464,401, entitled “Elasticized Disposable Training Pant havingDifferential Extensibility,” which issued on Sep. 21, 1993, to Hasse;U.S. Pat. No. 5,575,783, entitled “Absorbent Article with DynamicElastic Feature Comprising Elasticized Hip Panels,” which issued on Nov.19, 1996, to Clear; U.S. Pat. No. 5,779,691, entitled “Fastening Tapefor a Sanitary Article Particularly Disposable Diaper,” which issued onJul. 14, 1998, to Schmitt; U.S. Pat. No. 5,143,679, entitled “Method forSequentially Stretching Zero Strain Stretch Laminate Web to ImpartElasticity thereto Without Rupturing the Web,” which issued on Sep. 1,1992, to Weber; U.S. Pat. No. 4,834,741, entitled “Diaper with ElasticWaist Band Elastic,” which issued on May 30, 1989, to Sabee; and U.S.Pat. No. 4,968,313, entitled “Diaper with Elastic Waist Band Elastic,”which issued on Nov. 6, 1989, to Sabee.

An advantage of the present invention is that the path length of thedeformation zone can be easily adjusted to be several times greater inlength than processes of the prior art. The depth of engagement of theintermeshing teeth and grooves can be set to accommodate web speed,which is the speed the web flows in the machine direction duringprocessing. Specifically, it is often desirable to increase the pathlength of the deformation zone with increasing line speed. This is doneso that the incremental stretching of the web is performed over a longerdistance, and hence over a longer period of time, in spite of theincreased web speed. The action of increasing the deformation zone pathlength for increasing web speeds can be used to offset the deleteriouseffects of high speed activation noted in the prior art, such as inaforementioned U.S. Pat. No. 5,143,679 issued to Weber et al. Such priorart ring rolling, accomplished with intermeshing cylindrical rolls,provides a deformation zone(s) having only a fixed path length, fullydetermined only by the size of the rolls and the required degree ofengagement.

Table I demonstrates how the ring roll diameter increases significantlyfor deformation path lengths exceeding 1.0 inches (0.025 meters) inlength. For instance, providing a deformation zone path length of 2.0inches (0.051 meters) would require a ring roll diameter of about 96inches (2.44 meters). A deformation path length of 39 inches (1 meter)would require a set of ring rolls of the prior art approaching 1kilometer in diameter. Therefore, it can be seen that larger deformationpath lengths, while often being desirable to reduce the deleteriouseffects of higher web speeds, would require use of impractical ring rollsizes. The Table also shows the estimated machine direction length (MDLength) of the dual activation belt (belt/belt) and single activationroll and activation belt (belt/Roll) apparatus for each correspondingdeformation zone path length.

TABLE I Range of Corresponding Deformation Ring Roll Estimated EstimatedZone Path Diameter @ Belt/Belt Belt/Roll Length 0.080″ DOE MD Length* MDLength* (m/in) (m/in) (m/in) (m/in) 0.012/0.48 0.144/5.7  0.402/15.80.395/15.6 0.025/0.99 0.610/24  0.415/16.3 0.401/15.8 0.050/2.0 2.44/96  0.440/17.3 0.411/16.2 0.100/3.9  9.91/390 0.490/19.3 0.432/17.00.290/11.5  82.5/3250 0.680/26.8 0.513/20.2 1.00/39    991/39000 1.39/54.7 0.815/32.1  3.00/118 — 3.39/133  1.66/65.4  6.00/236 —6.39/252  2.94/116 *MD Length is defined as the minimum space in themachine direction required for the apparatus.

Assumptions:

-   -   1. Belt/Belt MD length=the deformation zone path length plus        0.39 m for accompanying rollers.    -   2. Belt/Roll MD length=the roll diameter plus 0.39 m for the        accompanying back-up rollers.    -   3. Maximum Belt/Roll deformation zone path length=0.75*roll        circumference (i.e. 270 degree of wrap)

The beneficial effects of increased deformation zone path lengthproduced via the methods and apparatus of the present invention can befurther described in the graphs shown in FIG. 10A and FIG. 10B. Assuminga web speed of about 500 ft/min (2.54 meters per second), a belt pitchof 0.060 inches (1.52 mm) and a depth of engagement of 0.079 inches (2.0mm), the graph in FIG. 10A shows the depth of engagement vs. the time ofengagement comparing a ring roll system of the prior art to apparatus ofthe present invention. The plot illustrates how the path length of thedeformation zone for the apparatus of the present invention can be sizedand arranged to provide a gradual linear increase in depth of engagementcompared to a rapid non linear increase associated with the shorterdeformation zone path length of ring rolls. The resulting effect ofthese differing path lengths is shown in the graph of FIG. 10B, in whichthe corresponding rate of activation, or rate of engagement, is plottedvs. depth of engagement. The graph demonstrates how ring roll processesof the prior art induce very high rates of strain in the materialcompared to the very low (and in this case) constant rate of strainapplied by methods and processes of the present invention. Thissignificant decrease in the rate of engagement results in acorrespondingly reduced rate of deformation to the web, whicheffectively minimizes or eliminates the aforementioned deleteriouseffects that high activation rates have on many web materials.

Another means for deforming a web which can be performed using theactivation members of the present invention is a process commonlyreferred to as a “SELF” or “SELF'ing” process, in which SELF stands forStructural Elastic Like Film. While the process was originally developedfor deforming polymer film to have beneficial structuralcharacteristics, it has been found that the SELF'ing process can be usedto produce beneficial structures in nonwoven webs.

Referring to FIG. 11, there is shown a configuration of activationmembers for use in a SELF process that can be employed to expandportions of a nonwoven web in the web thickness dimension, by expandingportions of the web out of the X-Y plane in the Z-direction. As shown inFIG. 11, one activation member 64 includes a plurality oflongitudinally-extending, laterally-spaced teeth 52 and grooves 54.Activation member 62 includes a plurality of longitudinally extending,laterally-spaced teeth 68 wherein portions of the teeth 68 of activationmember 62 have been removed to form notches 66 that define a pluralityof spaced teeth 68. As shown in FIG. 11, notches 66 on respectivetransversely adjacent teeth 68 can be aligned laterally to define aplurality of spaced groups of notched regions about the surface of theactivation member 62. The respective laterally-extending groups ofnotched regions each extend parallel to the cross machine direction CDof the activation member 62. Teeth 68 can have a tooth heightcorresponding to tooth height TH, and a tooth pitch corresponding to thetooth pitch P as previously described in reference to FIG. 8.

As a web passes through a deformation zone formed by activation membersin a SELF process, the teeth 68 of activation member 62 press a portionof the web out of plane to cause permanent, localized Z-directiondeformation of the web. But the portion of the web that passes betweenthe notched regions 66 of activation member 62 and the teeth 68 ofactivation member 62 will be substantially unformed in the Z-direction,i.e., the nonwoven web will not be deformed or stretched in that area tothe same degree as that of the toothed regions, and can remainsubstantially planar, while the portions of the web passing betweentoothed regions of activation member 62 and the teeth 52 of activationmember 64 can be deformed or stretched beyond the elastic limit of thenonwoven, resulting in a plurality of deformed, raised, rib-likeelements.

Referring now to FIG. 12, there is shown a schematic representation of aportion of a SELF'ed nonwoven web 70 after it has passed between a pairof opposed, interengaged activation members 62 and 64 of a SELF process,the activation members having the tooth configurations similar to thatshown in FIG. 11. SELF'ed nonwoven web 70 includes a network of distinctregions. The network includes at least a first region 72, a secondregion 84, and a transitional region 76, which is at the interfacebetween the first region 72 and the second region 84. SELF'ed nonwovenweb 70 also has a first surface 78 and an oppositely-facing secondsurface 80. In the embodiment shown in FIG. 12, SELF'ed nonwoven web 70includes a plurality of substantially flat spaced first regions 72 and aplurality of alternating rib-like elements forming the second region 84.

In the embodiment shown in FIG. 12, first regions 72 are substantiallyplanar. That is, the material within first regions 72 is substantiallyflat and is in substantially the same condition after the modificationstep undergone by a nonwoven web by passage between activation members62 and 64 shown in FIG. 11 as it was in before the web was passedbetween the activation members.

In addition to the surface pattern illustrated in FIG. 12 in the form ofrib-like elements each having substantially equal lengths and arrangedin rows to define generally rectangular areas of deformation separatedby linear first regions 72, the desired formation of a nonwoven web can,if desired, be effected by other activation member tooth and grooveconfigurations that can cause localized stretching and/or deformation ofthe nonwoven material. For example, as shown in FIG. 13, instead ofspaced rectangular arrays of rib-like elements the deformation patterncan be in the form of rib-like elements defining an array of spaced,diamond-shaped second regions 74 with intervening undeformed firstregions 72. Each such diamond-shaped second region 74 is defined byalternating rib-like elements 84 and intervening valleys 86. Examples ofmethods and apparatus for formation of such diamond-shaped elements aredisclosed in U.S. Pat. No. 5,650,214, entitled, “Sheet MaterialsExhibiting Elastic-Like Behavior and Soft, Cloth-Like Texture,” whichissued on Jul. 22, 1997, to Barry J. Anderson, et al., and U.S. Pat. No.6,383,431, entitled, “Method of Modifying a Nonwoven Fibrous Web For Useas a Component of a Disposable Absorbent Article,” which issued May 7,2002, to Dobrin, et al.

As shown in FIG. 14, the deformation pattern can also be in the form ofrib-like elements 84 that together define an array of spaced,circularly-shaped second regions 74. Each such circular element can bedefined by appropriately spaced, varying-length rib-like elements 84 andintervening valleys 86. Between respective circularly-shaped secondregions 74 are unformed intervening first regions 72. As will beapparent to those skilled in the art, other deformation patterns canalso be employed, if desired, such as those illustrated and described inU.S. Pat. No. 5,518,801, entitled “Sheet Materials ExhibitingElastic-Like Behavior,” which issued on May 21, 1996, to Charles W.Chappell et al. Other patents issued to Chappell include U.S. Pat. No.5,691,035 entitled “Web Materials Exhibiting Elastic-like Behavior,”issued Nov. 25, 1997; U.S. Pat. No. 5,723,087 entitled “Web MaterialsExhibiting Elastic-like Behavior,” issued Mar. 3, 1998; U.S. Pat. No.5,891,544 entitled “Web Materials Exhibiting Elastic-like Behavior”issued Apr. 6, 1999; U.S. Pat. No. 5,916,663 entitled “Web MaterialsExhibiting Elastic-like Behavior,” issued Jun. 29, 1999; and U.S. Pat.No. 6,027,483 entitled “Web Materials Exhibiting Elastic-like Behavior”issued Feb. 22, 2000.

Another means for deforming a web which can be performed using theactivation members of the present invention is a process that can bestbe described as “micro-SELF”. Micro-SELF is a process that is similar inapparatus and method to that of the SELF process described withreference to FIG. 11. The main difference between SELF and micro-SELF isthe size and dimensions of the teeth 68 on the toothed activationmember, i.e., the micro-SELF activation member 82 in FIG. 15, whichcorresponds to activation member 62 of FIG. 11. The micro-SELFactivation member 82 can be one of the activation members forming thedeformation zone in a preferred configuration having one patternedactivation member, e.g., micro-SELF activation member 82, and onenon-patterned grooved activation member (not shown). However, in certainembodiments it may be preferable to use two micro-SELF activationmembers 82 having either the same or differing patterns, in the same ordifferent corresponding regions of the respective activation members.Such an apparatus can produce webs with deformations that, in nonwovenwebs, can be described as tufts protruding from one or both sides of theprocessed web. The tufts can be closely spaced, but at least at theirbase can be spaced apart sufficiently to define void regions betweentufts.

As shown in the partial perspective view of FIG. 15 and the enlargedpartial perspective view of FIG. 16, the teeth 68 of a micro-SELFactivation member 82 have a specific geometry associated with theleading and trailing edges of teeth 68 that permit the teeth toessentially “punch” through the nonwoven web as opposed to, in essence,deforming the web into bumps or teeth as shown in FIGS. 12-14. In someembodiments of a nonwoven web, the teeth 68 urge fibers out-of-plane andto form what can be described as “tufts” or loops of fibers. In oneembodiment, the web is punctured, so to speak, by the teeth 68 pushingthe fibers through to form tufts or loops. Therefore, unlike the“tent-like” rib-like elements of SELF webs which each have continuousside walls associated therewith, i.e., a continuous “transition zone,”the tufts or loops forced out-of-plane in a micro-SELF process can havea discontinuous structure associated with the side wall portions of theZ-direction deformations. Additionally, when utilized for relativelyhigh basis weight absorbent core materials, the “tufting” can besomewhat invisible as fibers are urged out of the plane in a Z-directionwith respect to one of the web surfaces, the Z-direction deformation maybe muted or non-existent in the other web surface. Further, when alaminate material is involved, the Z-direction deformations of one webmaterial may be pushed into and “hidden” by the second material of thelaminate, such that the “tufting” is essentially invisible to the nakedeye.

As shown in FIGS. 15 and 16, each tooth 68 has a tooth tip 96, a leadingedge LE and a trailing edge TE. The tooth tip 96 is elongated and has agenerally longitudinal orientation. It is believed that to get tufted,looped tufts in the processed web, the LE and TE should be very nearlyorthogonal to the local peripheral surface 90 of activation member 82.As well, the transition from the tip 96 and LE or TE should be a sharpangle, such as a right angle, having a sufficiently small radius ofcurvature such that teeth 68 push through the web at the LE and TE.Without being bound by theory, it is believed that having relativelysharply angled tip transitions between the tip 96 of tooth 68 and the LEand TE permits the teeth 68 to punch through nonwoven webs “cleanly”,that is, locally and distinctly, so that one side of the resulting webcan be described as “tufted” or otherwise “deformed.”

The teeth 68 of a micro-SELF activation member 82 can have a uniformlength dimension TL measured generally from the leading edge LE to thetrailing edge TE at the tooth tip 96 of about 1.25 mm and are uniformlyspaced from one another circumferentially by a distance TD of about 1.5mm. For making a terry-cloth web from a web having a total basis weightin the range of about 60 to about 100 gsm, teeth 68 can have a length TLranging from about 0.5 mm to about 3 mm and a spacing TD from about0.020 inches (0.5 mm) to about 0.118 inches (3 mm), a tooth heightranging from about 0.020 inches (0.5 mm) to about 0.200 inches (5 mm),and a pitch between about 0.040 inches (1 mm) and about 0.200 inches (5mm). Depth of engagement can be from about 0.020 inches (0.5 mm) toabout 0.200 inches (5 mm) (up to a maximum equal to tooth height). Ofcourse, depth of engagement, pitch, tooth height, TD, and TL can bevaried independently of each other to achieve a desired size, spacing,and area density of web deformations as disclosed in co-pending,commonly owned patent applications US 2004/0265534A1, filed Dec. 16,2003 and US 2005/0123726A1, filed Nov. 3, 2004.

Using the micro-SELF activation members according to the presentinvention, the strain rate in the deformation zone can be controlled toproduce web structures exhibiting different tuft and loop formations.For instance, for laminate structure comprising two relativelyinextensible materials, the strain rate in the deformation zone can becontrolled to vary from low to high as illustrated in the graph in FIG.17 providing tufts comprising taller loops with blown out tipsillustrated in FIG. 18A in comparison to smaller loops with blown outtips formed via high strain rate activation illustrated in FIG. 18B.Alternatively, for relatively inextensible materials with slightlydifferent extensibilities, varying the strain rate in the deformationzone from a high rate of strain to a low rate of strain as illustratedin the graph in FIG. 19 can result in one of the materials burstingearly on resulting in a blown out tip and the other material forming atall loop extending through the blown out tip illustrated in FIG. 20A incomparison to smaller loops with blown out tips formed via high strainrate activation illustrated in FIG. 20B.

Another means for deforming a web which can be performed using theactivation members of the present invention is a process that can bestbe described as “rotary knife aperturing” (RKA). In RKA, a process andapparatus using intermeshing activation members 92 similar to thatdescribed above with respect to SELF or micro-SELF activation members isutilized, as shown in FIG. 21. As shown, the RKA process differs fromSELF or micro-SELF in that the relatively flat, elongated teeth of aSELF or micro-SELF activation member have been modified to be generallypointed at the distal end. Teeth 68 can be sharpened to cut through aswell as deform nonwoven web 34 to produce a three-dimensionallyapertured web 94 as shown in FIG. 21. In other respects such as toothheight, tooth spacing, pitch, depth of engagement, and other processingparameters, RKA and the RKA apparatus can be the same as described abovewith respect to SELF or micro-SELF.

FIG. 22 shows a portion of one embodiment of an RKA toothed activationmember having a plurality of teeth 68 useful for making an apertured web94. An enlarged view of the teeth 68 is shown in FIGS. 23 A and 23B. Asshown in FIG. 23A, each tooth 68 has a base 111, a tooth tip 96, aleading edge LE and a trailing edge TE. The tooth tip 96 can begenerally pointed, blunt pointed, or otherwise shaped so as to stretchand/or puncture the web 34. Teeth 68 can have generally flattened,blade-like shape. Teeth 68 can have generally flattened distinct sides98. That is, as opposed to round, pin-like shapes that are generallyround in cross section, teeth 68 can be elongated in one dimension,having generally non-round, elongated cross-sectional configurations.For example, at their base, teeth 68 can have a tooth length TL and atooth width TW exhibiting a tooth aspect ratio AR of TL/TW of at least2, or at least about 3, or at least about 5, or at least about 7, or atleast about 10 or greater. In one embodiment, the aspect ratio AR ofcross-sectional dimensions remains substantially constant with toothheight.

In one embodiment of an RKA toothed activation member, teeth 68 can havea uniform length dimension TL of about 0.049 inches (1.25 mm) measuredgenerally from the leading edge LE to the trailing edge TE at the base111 of the tooth 68, and a tooth width TW of about 0.012 inches (0.3 mm)which is the longest dimension measured generally perpendicularly to thelength dimension at the base. Teeth can be uniformly spaced from oneanother by a distance TD of about 0.059 inches (1.5 mm). For making asoft, fibrous three-dimensional apertured web from a web having a basisweight in the range of from about 5 gsm to about 200 gsm, teeth 68 canhave a length TL ranging from about 0.5 mm to about 3 mm, a tooth widthTW of from about 0.3 mm to about 1 mm, and a spacing TD from about 0.5mm to about 3 mm, a tooth height TH ranging from about 0.5 mm to about10 mm, and a pitch P between about 1 mm (0.040 inches) and 2.54 mm(0.100 inches). Depth of engagement E can be from about 0.020 inches(0.5 mm) to about 0.200 inches (5 mm) (up to a maximum approaching thetooth height TH).

Of course, E, P, TH, TD and TL can each be varied independently of eachother to achieve a desired size, spacing, and area density of apertures(number of apertures per unit area of apertured three-dimensionallyapertured web 94). For example, to make apertured films and nonwovenssuitable for use in sanitary napkins and other absorbent articles, toothlength TL at the base can range between about 0.08 inches (2.032 mm) toabout 0.15 inches (3.81 mm); tooth width TW can range from about 0.02inches (0.508 mm) to about 0.05 inches (1.27 mm); tooth spacing TD canrange from about 0.039 inches (1.0 mm) to about 0.076 inches (1.94 mm);pitch P can range from about 0.044 inches (1.106 mm) to about 0.100inches (2.54 mm); and tooth height TH can be from about 0.08 inches(2.032 mm) to about 0.27 inches (6.858 mm). Depth of engagement E can befrom about 0.020 inches (0.5 mm) to about 0.200 inches (5 mm). Theradius of curvature R of the tooth tip 96 shown in FIG. 23B can be from3.937×10⁻⁵ inches 0.001 mm to about 3.9×10⁻⁴ inches (0.009 mm). Withoutbeing bound by theory, it is believed that tooth length TL at the basecan range between about 0.01 inches (0.254 mm) to about 0.5 inches (12.7mm); tooth width TW can range from about 0.01 inches (0.254 mm) to about0.2 inches (5.08 mm); tooth spacing TD can range from about 0.0 mm toabout 1.0 inches (25.4 mm) (or more); pitch P can range from about 0.044inches (1.106 mm) to about 0.3 inches (7.62 mm); tooth height TH canrange from 0.01 inches (0.254 mm) to about 0.709 inches (18 mm); anddepth of engagement E can range from 0.01 inches (0.254 mm) to about0.25 inches (6.35 mm). For each of the ranges disclosed, it is disclosedherein that the dimensions can vary within the range in increments of3.937×10⁻⁵ (0.001 mm) from the minimum dimension to the maximumdimension, such that the present disclosure is teaching the range limitsand every dimension in between in 3.937×10⁻⁵ inch (0.001 mm) increments(except for radius of curvature R, in which increments are disclosed asvarying in 3.937×10⁻⁵ inch (0.0001 mm) increments).

RKA teeth can have other shapes and profiles and the RKA process can beused to aperture fibrous webs, as disclosed in co-pending, commonlyowned patent applications US 2005/0064136A1, filed Aug. 6, 2004, US2006/0087053A1, filed Oct. 13, 2005, and US 2005/021753 filed Jun. 21,2005.

The apparatus of the present invention may be arranged sequentiallyand/or intermixed with aforementioned apparatus described in the priorart. For example, a first apparatus of the present invention can be usedto incrementally stretch the web in the cross machine direction followedby a second apparatus which can be used to incrementally stretch the webin the machine direction.

The dimensions and values disclosed herein are not to be understood asbeing strictly limited to the exact numerical values recited. Instead,unless otherwise specified, each such dimension is intended to mean boththe recited value and a functionally equivalent range surrounding thatvalue. For example, a dimension disclosed as “40 mm” is intended to mean“about 40 mm”

All documents cited in the Detailed Description of the Invention are, inrelevant part, incorporated herein by reference; the citation of anydocument is not to be construed as an admission that it is prior artwith respect to the present invention. To the extent that any meaning ordefinition of a term in this document conflicts with any meaning ordefinition of the same term in a document incorporated by reference, themeaning or definition assigned to that term in this document shallgovern.

While particular embodiments of the present invention have beenillustrated and described, it would be obvious to those skilled in theart that various other changes and modifications can be made withoutdeparting from the spirit and scope of the invention. It is thereforeintended to cover in the appended claims all such changes andmodifications that are within the scope of this invention.

What is claimed is:
 1. A method of incrementally stretching a web, themethod comprising the steps of: a. providing a web; b. providing asingle activation member comprising a plurality of teeth and grooves; c.providing an activation belt comprising a plurality of teeth and groovesthat complement the plurality of teeth and grooves of the singleactivation member; d. forming a deformation zone between the activationbelt and the single activation member wherein the plurality of teeth andgrooves of the single activation member engage the plurality of teethand grooves of the activation belt at a controlled depth of engagementcapable of increasing linearly over the deformation zone; and e.conveying the web through the deformation zone wherein the web isincrementally stretched.
 2. The method according to claim 1 wherein thesingle activation member comprises a single activation roll having aplurality of circumferential teeth and grooves.
 3. The method accordingto claim 2 wherein the deformation zone is formed between a firstsection of a plurality of teeth and grooves of the activation belt andan arcuate section of a plurality of circumferential teeth and groovesof the single activation roll.
 4. The method according to claim 3wherein the depth of engagement is controlled by a series of back-uprollers arranged along the deformation zone forcing the first section ofthe plurality of teeth and grooves of the activation belt intoengagement with the arcuate section of the plurality of circumferentialteeth and grooves of the single activation roll.
 5. The method accordingto claim 4 wherein the depth of engagement is controlled to increaselinearly over at least a portion of the deformation zone.
 6. The methodaccording to claim 1 wherein the activation belt comprises a firstactivation belt and the single activation member comprises a secondactivation belt comprising a plurality of teeth and grooves thatcomplement and engage the plurality of teeth and grooves of the firstactivation belt at the depth of engagement in the deformation zone. 7.The method according to claim 6 wherein the deformation zone is formedbetween a first section of a plurality of teeth and grooves of the firstactivation belt and a second section of a plurality of teeth and groovesof the second activation belt, wherein the first section of the firstactivation belt is supported by a first set of rollers and the secondsection of the second activation belt is supported by a second set ofrollers and wherein the first set of rollers and the second set ofrollers are arranged in the deformation zone to force the first sectionof the plurality of teeth and grooves of the first activation belt intoengagement with the second section of the plurality of teeth and groovesof the second activation belt and to control the depth of engagementtherebetween.
 8. The method according to claim 7 wherein the depth ofengagement is controlled to increase linearly over at least a portion ofthe deformation zone.
 9. An apparatus for incrementally stretching aweb, the apparatus comprising: a. a single activation member comprisinga plurality of teeth and grooves; b. an activation belt comprising aplurality of teeth and grooves that complement the plurality of teethand grooves of the single activation member; and c. a deformation zoneformed between the activation belt and the single activation memberwherein the plurality of teeth and grooves of the single activationmember engage the plurality of teeth and grooves of the activation beltat a controlled depth of engagement capable of increasing linearly overthe deformation zone such that a web interposed between the activationbelt and the single activation member in the deformation zone isincrementally stretched.
 10. The apparatus according to claim 9 whereinthe single activation member comprises a single activation roll having aplurality of circumferential teeth and grooves.
 11. The apparatusaccording to claim 10 wherein the deformation zone is formed between afirst section of a plurality of teeth and grooves of the activation beltand an arcuate section of a plurality of circumferential teeth andgrooves of the single activation roll.
 12. The apparatus according toclaim 11 wherein the depth of engagement is controlled by a series ofback-up rollers arranged along the deformation zone supporting the firstsection of the plurality of teeth and grooves of the activation beltalong the arcuate section of the plurality of circumferential teeth andgrooves of the single activation roll.
 13. The apparatus according toclaim 12 wherein the depth of engagement is controlled to increaselinearly over at least a portion of the deformation zone.
 14. Theapparatus according to claim 9 wherein the activation belt comprises afirst activation belt and the single activation member comprises asecond activation belt comprising a plurality of teeth and grooves thatcomplement and engage the plurality of teeth and grooves of the firstactivation belt in the deformation zone at the depth of engagement. 15.The apparatus according to claim 14 wherein the deformation zone isformed between a first section of a plurality of teeth and grooves ofthe first activation belt and a second section of a plurality of teethand grooves of the second activation belt, wherein the first section ofthe first activation belt is supported by a first set of rollers and thesecond section of the second activation belt is supported by a secondset of rollers and wherein the first set of rollers and the second setof rollers are arranged to force the first section of the plurality ofteeth and grooves of the first activation belt into engagement with thesecond section of the plurality of teeth and grooves of the secondactivation belt and to control the depth of engagement therebetween. 16.The apparatus according to claim 15 wherein the depth of engagement iscontrolled to increase linearly over at least a portion of thedeformation zone.
 17. An apparatus for incrementally stretching a web,the apparatus comprising: a. a single activation roll comprising aplurality of circumferential teeth and grooves; b. an activation beltcomprising a plurality of teeth and grooves that complement theplurality of circumferential teeth and grooves of the single activationroll; c. a deformation zone having a path length formed between a firstsection of the activation belt and an arcuate section of the singleactivation roll wherein the plurality of circumferential teeth andgrooves of the single activation roll engage the plurality of teeth andgrooves of the activation belt at a depth of engagement; and d. a seriesof back-up rollers supporting the first section of the activation beltalong the path length, forcing the plurality of teeth and grooves of theactivation belt into engagement with the plurality of circumferentialteeth and grooves of the single activation roll and controlling thedepth of engagement therebetween.
 18. The apparatus according to claim17 wherein at least two of the back-up rollers are independentlyadjustable to control the depth of engagement and wherein the depth ofengagement can be controlled to increase linearly over at least aportion of the deformation zone.
 19. An apparatus for incrementallystretching a web, the apparatus comprising: a. a first activation beltcomprising a plurality of teeth and grooves; b. a second activation beltcomprising a plurality of teeth and grooves that complement theplurality of teeth and grooves of the first activation belt; c. adeformation zone having a path length formed between a first section ofthe first activation belt and a second section of the second activationbelt wherein the plurality of teeth and grooves of the first activationbelt engage the plurality of teeth and grooves of the second activationbelt at a depth of engagement; and d. a first set of rollers supportingthe first section of the first activation belt along the path length anda second set of rollers supporting the second section of the secondactivation belt along the path length wherein the first set of rollersand the second set of rollers are arranged to force the teeth andgrooves of the first activation belt into engagement with the teeth andgrooves of the second activation belt and to control the depth ofengagement therebetween.
 20. The apparatus according to claim 19 whereinat least two rollers disposed at different locations along a path lengthof the deformation zone are independently adjustable to change the depthof engagement and wherein the depth of engagement can be controlled toincrease linearly over at least a portion of the deformation zone. 21.An apparatus for incrementally stretching a web wherein the apparatusoccupies a space in a machine direction which is less than about 3.0meters, the apparatus comprising: a. a single activation roll comprisinga plurality of circumferential teeth and grooves; b. an activation beltcomprising a plurality of teeth and grooves that complement theplurality of circumferential teeth and grooves of the single activationroll; c. a deformation zone having a path length of at least about 0.05meters formed between the activation belt and the single activation rollwherein the plurality of circumferential teeth and grooves of the singleactivation roll engage the plurality of teeth and grooves of theactivation belt at a depth of engagement; and d. a series of back-uprollers arranged along the path length of the deformation zone forcingthe activation belt into engagement with the single activation roll andcontrolling the depth of engagement therebetween.
 22. An apparatus forincrementally stretching a web wherein the apparatus occupies a space ina machine direction which is less than about 3.0 meters, the apparatuscomprising: a. a first activation belt comprising a plurality of teethand grooves; b. a second activation belt comprising a plurality of teethand grooves that complement the plurality of teeth and grooves of thefirst activation belt; c. a deformation zone having a path length of atleast about 0.05 meters formed between a first section of the firstactivation belt and a second section of the second activation beltwherein the plurality of teeth and grooves of the first activation beltengage the plurality of teeth and grooves of the second activation beltat a depth of engagement; and d. a first set of rollers supporting thefirst section of the first activation belt and a second set of rollerssupporting the second section of the second activation belt wherein thefirst set of rollers and the second set of rollers are arranged to forcethe teeth and grooves of the first activation belt into engagement withthe teeth and grooves of the second activation belt and to control thedepth of engagement therebetween.
 23. An apparatus for incrementallystretching a web, the apparatus comprising: a. a single activationmember comprising a plurality of teeth and grooves; b. an activationbelt comprising a plurality of teeth and grooves that complement theplurality of teeth and grooves of the single activation member, whereinthe single activation member and the activation belt occupy a space in amachine direction of less than 3.0 meters; and c. a deformation zoneformed between the activation belt and the single activation memberwherein the plurality of teeth and grooves of the single activationmember engage the plurality of teeth and grooves of the activation beltat a controlled depth of engagement along a path length of at leastabout 0.15 meters.
 24. A method of incrementally stretching a web, themethod comprising the steps of: a. providing a web; b. providing asingle activation member comprising a plurality of teeth and grooves; c.providing an activation belt comprising a plurality of teeth and groovesthat complement the plurality of teeth and grooves of the singleactivation member; d. forming a deformation zone between the activationbelt and the single activation member wherein the plurality of teeth andgrooves of the single activation member engage the plurality of teethand grooves of the activation belt at a controlled depth of engagement,and wherein the deformation zone has a path length of at least about0.15 meters; and e. conveying the web in a machine direction through thedeformation zone wherein the single activation member and the activationbelt occupy a space in the machine direction of less than 3.0 meters.